Resumo em Inglês:

This work addresses wireless capacity models and capacity consumption models for 3G WCDMA system analysis. Uplink and downlink capacities are viewed as multiple heterogeneous circuit-switched and packet-switched pools of various bit rate channels, wherein traffic channels and control channels contend for the same capacity within a cell. An individual user's consumption of capacity is formulated as a function of the user's traffic class, activity factor and negotiated QoS. Simulation based analysis, of resource management algorithms that employ admission control and channel rate- and type-switching, are undertaken to compare results obtained using the proposed capacity and capacity consumption models to that obtained using existing homogeneous models. The primary results demonstrate that differentiating between channel modes, giving consideration to control channel utilization, and giving consideration to user's service type can each significantly impact the results and conclusions drawn from resource management protocol analysis.

Resumo em Inglês:

As networks with mobile devices becorne commonplace, many new applications for those networks arisc, including some that require coordination among groups of mobile clients. One basic tool for implementing coordination is reliable multicast, where delivery of a multicast message is atomic, i.e. cither all or none of the group members deliver the message. While several multicast protocols have been proposed for mobile networks, only a few works have considered reliable multicats. In this paper we present and compare two protocols based on Two-Phase-Commit that implement reliable multicast for structured mobile networks. Protocol iAM²C is a variant of protocol AM2C that employs a two-level hierarchical location management scheme to locate and route messages to the mobile hosts addressed by a multicast. Although hierarchical location management is not new in the context of mobile and cellular networks, we are unaware of any other work which combines hierarchical location management with protocols for reliable multicast. We have prototyped, simulated and evaluated both protocols using the MobiCS simulation enviromment. Our experiments indicate that despite some overhead incurred by the location management and the additional level of message redirection, iAM2C is more efficient than the AM² C protocol and scales well with the size of the wired network infra-structure.

Resumo em Inglês:

The data traffic in wireless networks for the third generation (3G) mobile telecommunication systems should take into account a variety of services (voice, data, video) and environments (e.g.: private, outdoors, indoors) as well as the user mobility behavior. A good evaluation of measures of performance can help a system designer to make its strategic decisions concerning cell size and the number of channel frequencies allocated to each cell. In this paper we present an analysis of data services in a third generation mobile telecommunication networks based on simulation. In addition, we illustrate the need for a simulation in order to characterize the mix of several traffic types for capacity and quality of service (QoS) planning. We use the distributions heavy tailed Weibull and Pareto to simulate respectively, the data traffic and the resource occupation time for data service. Finally, we also comment some simulation results of third generation services where we analyze the QoS parameters of a mobile network, such as channel occupation time, handoff, new call blocking probabilities and traffic in Erlangs.

Resumo em Inglês:

The adoption of the Internet Protocol in mobile and wireless technologies has considerably increased the number of hosts that can potentially access the global Internet. IPv6 is considered the long term solution for the IPv4 address shortage problem, but the transition from IPv4 to IPv6 is supposed to be very gradual. Therefore, there will be a long time during which both protocol versions will coexist. To facilitate transition, the IETF has set up a work group called NGTRANS (Next Generation TRANSition) which specifies mechanisms for supporting interoperability between IPv4 and IPv6. This paper describes a new approach for implementing mobile networks with global Internet connectivity using transition mechanisms. It consists in virtually assigning IPv6 addresses to IPv4 hosts without modifying end-user devices by introducing a transparent gateway in the mobile network. The mobile hosts with virtual IPv6 addresses are uniquely addressed through the global IPv4 Internet by using IPv6 addresses from the standard 6to4 addressing scheme or Fully Qualified Domain Names (FQDN). This "extended" transition mechanism permits to deploy mobile networks with global Internet connectivity without requiring public IPv4 addresses, using legacy IPv4 user devices. The mobile hosts with virtual IPv6 addresses can communicate to other hosts with virtual IPv6 addresses or with "true " IPv6 networks.

Resumo em Inglês:

In this paper we show that programming languages can be translated into recurrent (analog, rational weighted) neural nets. Implementation of programming languages in neural nets turns to be not only theoretical exciting, but has also some practical implications in the recent efforts to merge symbolic and sub symbolic computation. To be of some use, it should be carried in a context of bounded resources. Herein, we show how to use resource bounds to speed up computations over neural nets, through suitable data type coding like in the usual programming languages. We introduce data types and show how to code and keep them inside the information flow of neural nets. Data types and control structures are part of a suitable programming language called NETDEF. Each NETDEF program has a specific neural net that computes it. These nets have a strong modular structure and a synchronization mechanism allowing sequential or parallel execution of subnets, despite the massive parallel feature of neural nets. Each instruction denotes an independent neural net. There are constructors for assignment, conditional and loop instructions. Besides the language core, many other features are possible using the same method.